Apparatus and method for multi-layer injection molding

ABSTRACT

An injection molding apparatus and method for multi-layer molding of preforms and closures has a central melt channel, an annular melt channel radially spaced from the central melt channel, and an annular ring channel surrounding the central melt channel. The central melt channel has a first portion for flow of a first material, a second portion for flow of the first material and a second material, and a flow extension connecting the first portion and the second portion. The flow extension has a flow opening in communication with the annular ring channel for flow of the second material. The apparatus and method also include a cavity for receiving flow of the first material and the second material from the central melt channel, and for receiving flow of a third material from the annular melt channel. In addition, the apparatus and method include a first melt passage in communication with the annular melt channel, a second melt passage in communication with the annular ring channel, and a third melt passage in communication with the central channel.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/271,835 filed Mar. 18, 1999, now pending and specificallyincorporated in its entirety herein by reference.

FIELD OF INVENTION

The present invention relates to multi-layer products, and an apparatusand method for the injection molding of same. More specifically, itrelates to a four-layer bottle preform and closure, and an apparatus andmethod for injection molding of same.

BACKGROUND OF THE INVENTION

Multi-cavity injection molding apparatus for making multi-layer moldedproducts, such as protective containers for food, preforms for beveragebottles, and closures, are well-known. One or more layers of onematerial are typically molded within, or together with, one or morelayers of another material, to form the molded product. At least one ofthese layers is usually a barrier layer formed from a barrier materialto protect the contents of the molded product. Since the barriermaterial is expensive, typically only a very thin barrier layer is usedin the molded product. It is also generally desirable to have this thinbarrier layer uniformly and evenly distributed (i.e., well-balanced)throughout the molded product to provide the proper protection for thecontents of the molded product.

An example of an injection molding apparatus used to make four-layerpreforms with thin barrier layers is disclosed in U.S. Pat. No.4,990,301 to Krishnakumar et al. Krishnakumar et al. disclose aninjection molding device having multiple and selective melt inlets,passages, channels, and gates, requiring different manifoldconfigurations, for forming multiple layer preforms. In particular,Krishnakumar et al. disclose the use of one large central melt passageand three small annular melt passages flowing into a central channelthat opens into a cavity for multi-layer preforms. Depending on theapplication, either the large central melt passage or one of the threesmall annular melt passages may be chosen for a barrier material.Krishnakumar et al. inject the barrier material from a selected passageinto the cavity, either directly against a cooled portion of preformmaterial previously disposed in the cavity, or after injecting a hotportion of preform material from another passage, in addition to thecooled portion, into the cavity.

There are several problems with the device disclosed by Krishnakumar etal. First, the injection molding device disclosed by Krishnakumar et al.uses multiple melt inlets, passages, channels, and gates that requireseveral different configurations for the same manifold, depending on theapplication, to make multi-layer preforms. As a result, the injectionmolding device of Krishnakumar et al. is complex and expensive to bothmanufacture and operate. Second, injecting a barrier material directlyagainst a cooled portion of preform material previously disposed in acavity often results in an uneven, or interrupted, barrier layer thatdoes not properly protect the contents of the molded preform. An alteredand non-uniform barrier layer may also present problems with blowing outthe preform. Third, injecting a barrier material only after injecting ahot portion of preform material, in addition to the cooled portion, intoa cavity adds additional time to the injection cycle or production timefor the preforms.

Finally, the injection molding device disclosed by Krishnakumar et al.uses large and small passages for the flow of barrier material. Thelarge passage can be problematic, since it can retain too much barriermaterial at a high temperature, thereby causing the degradation of thebarrier material. On the other hand, the small passages can cause highpressure drops for the barrier material as it enters the cavity, therebydamaging or washing out the preform material already in the cavity.

Another example of an injection molding apparatus used to makefour-layer preforms with thin barrier layers is disclosed in U.S. Pat.No. 5,141,695 to Nakamura. Like Krishnakumar et al., Nakamura disclosesa method to produce a three material, four layer preform, where preformmaterial is injected first through an annular melt channel, and barrierlayer is injected later from a separate annular melt channelsimultaneously with a mixture of preform and barrier material injectedthrough a central melt channel. Besides using multiple annular meltchannels, which add to the complexity and expense of the injectionmolding apparatus, the method disclosed by Nakamura positions the thinbarrier layer directly against the cooled portion of preform materialalready in the cavity. As previously explained, this arrangement resultsin an uneven, non-uniform, and unbalanced barrier layer within thepreform. In addition, the small annular melt channel for the barriermaterial used in Nakamura's method causes a high pressure drop as thebarrier material enters the cavity, thereby potentially causing damageto the preform material already in the cavity.

Accordingly, it would be desirable to have an apparatus and method forinjection molding of four-layer preforms or closures that overcomes theproblems associated with the prior art by not having multiple meltinlets, passages, channels, and gates, and by having a singleconfiguration for each of its manifolds. An injection molding apparatusand method for injection molding of four-layer preforms or closureswithout multiple melt inlets, passages, channels, and gates would berelatively simpler and less expensive, both to manufacture and operate.

It would also be desirable to have an apparatus and method for injectionmolding of four-layer preforms or closures that does not inject abarrier material either directly against a cooled portion of one preformmaterial previously disposed in a cavity, or after injecting a hotportion of another preform material, in addition to the cooled portion,into the cavity. Such an apparatus and method would provide four-layerpreforms or closures with more evenly and uniformly distributed barrierlayers, and thus, better protection for the contents of the preforms orclosures, without increasing the cycle or production time for thepreforms or closures. Moreover, it would also be desirable to have anapparatus and method for injection molding of four-layer preforms orclosures that avoids the problems associated with large and/or smallpassages or channel for barrier material.

SUMMARY OF THE INVENTION

The present invention provides an injection molding apparatus formulti-layer molding comprising a central melt channel and an annularmelt channel radially spaced from the central melt channel. Theapparatus also comprises a first melt passage in communication with theannular melt channel, a second melt passage in communication with thecentral melt channel, and a third melt passage in communication with thecentral melt channel.

In addition, the present invention provides an injection moldingapparatus for multi-layer molding that comprises a central melt channelhaving a first portion for flow of a first material, a second portionfor flow of the first material and a second material, and a flowextension connecting the first portion and the second portion. The flowextension also has a flow opening. The apparatus further comprises anannular ring channel surrounding the central melt channel for flow ofthe second material. The annular ring channel is also in communicationwith the flow opening of the flow extension. The apparatus alsocomprises an annular melt channel radially spaced from the central meltchannel for flow of a third material.

Moreover, the present invention also provides an injection moldingapparatus for multi-layer molding comprising a central melt channel forflow of a first material and a second material, and an annular meltchannel radially spaced from the central melt channel for flow of athird material. The apparatus also comprises a cavity for receiving flowof the first material and the second material from the central meltchannel, and for receiving flow of the third material from the annularmelt channel.

The present invention also provides a method for injection molding ofmulti-layer products comprising the step of injecting afirst materialfrom a first melt passage into an annular melt channel radially spacedfrom a central melt channel. The method also comprises the step ofinjecting a second material from a second melt passage into the centralmelt channel. In addition, the method comprises the step of injecting athird material from a third melt passage into the central melt channel.

Furthermore, the present invention provides a method for injectionmolding of multi-layer products comprising the steps of injecting afirst material into a central melt channel having a first portion, asecond portion, and a flow extension connecting the first and secondportions, and injecting a second material into an annular ring channelsurrounding the central melt channel. The method also comprises the stepof injecting the second material from the annular ring channel into thecentral melt channel through a flow opening in the flow extension. Inaddition, the method comprises the steps of injecting a third materialinto an annular melt channel radially spaced from the central meltchannel, and joining the third material from the annular melt channelwith the first and second materials from the central melt channel.

The present invention also provides a method for injection molding ofmulti-layer products comprising the steps of injecting a first materialand a second material into a central melt channel, and injecting thefirst material and the second material from the central melt channelinto a cavity. In addition, the method comprises the steps of injectinga third material into an annular melt channel radially spaced from thecentral melt channel, and injecting the third material from the annularmelt channel into the cavity.

Additionally, the present invention provides an article of injectionmolding comprising an outer layer and an inner layer made from a firstmaterial from an annular melt channel. The article also comprises a corelayer between the outer and inner layers, and an intermediate layerbetween the inner layer and the core layer. The core layer is made froma second material from a central melt channel, and the intermediatelayer is made from a third material from the central melt channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a valve-gated injection moldingapparatus of the present invention for a four layer bottle preform.

FIG. 2 is an exploded cross-sectional view of a portion of a valvebushing of the injection molding apparatus of FIG. 1.

FIG. 3 is an exploded cross-sectional view of the portion of the valvebushing of FIG. 2.

FIGS. 4A-4E are exploded cross-sectional views of a nozzle and a cavityof the apparatus of FIG. 1, illustrating a method of the presentinvention.

FIG. 5 is an exploded cross-sectional view of FIG. 4C.

FIG. 6 is a cross-sectional view of a four layer bottle preform of thepresent invention.

FIG. 7 is a cross-sectional view of a four layer closure of the presentinvention.

FIG. 8 is a cross-sectional view of a thermal-gated injection moldingapparatus of the present invention for a four layer bottle preform.

FIG. 9 is a partial cross-sectional view of an alternative front meltdistribution manifold of the present invention.

FIG. 10 is a cross-sectional view of the thermal-gated injection moldingapparatus of FIG. 8 with melt mixers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawings, FIG. 1 shows a preferred embodiment of aportion of a valve-gated, multi-cavity injection molding apparatus 5 ofthe present invention with one nozzle 10 for molding four-layer bottlepreforms, closures, or other products by sequential and simultaneouscoinjection. Although only one nozzle is shown in FIG. 1 for ease ofillustration, any desirable number of nozzles (i.e., 12, 16, or 48) maybe used with the apparatus of the present invention. Preferably, eachadditional nozzle would have identical features to the nozzle 10 shownin FIG. 1 and described in detail below.

Besides the nozzle 10, the apparatus 5 also comprises a front meltdistribution manifold 18, a nozzle retainer plate 20, a back plate 24, acavity retainer plate 28, and a rear melt distribution manifold 94.Preferably, the nozzle retainer plate 20 and the back plate 24 arejoined together with a manifold plate 26. It should also be understoodthat the apparatus 5 can have a greater or fewer number of platesdepending upon the application, and for ease of illustration, only theabove-identified plates are shown in FIG. 1.

The nozzle retainer plate 20 is located about an end 87 of a manifoldlocator 88 between the front melt distribution manifold 18 and thecavity retainer plate 28. The nozzle retainer plate 20 has a nozzle seatopening 54 for receiving the nozzle 10. Preferably, there is a separatenozzle seat opening for every nozzle of the injection molding apparatus.The nozzle retainer plate 20 also preferably has an anti-rotational cam90 next to the nozzle 10 to prevent the nozzle from rotating within itsrespective nozzle seat opening 54.

The nozzle 10 has a body 12 with a front tip end 30 and a rear end 14.The nozzle is heated by an integral electrical heating element 58wrapped around the body 12. The heating element 58 has a terminal 60positioned near the rear end of the nozzle. The nozzle 10 also has aradial melt channel 64 extending from the rear end 14. In addition, thenozzle 10 has a nozzle gate seal 73 that is secured within the body 12of the nozzle 10 and forms the front tip end 30. Also, the nozzles gateseal 73 has a front opening 74 to allow material to pass out through thefront tip end 30 of the nozzle 10.

The nozzle also has a liner sleeve 70 secured within the nozzle gateseal 73. The liner sleeve 70 has a front opening 75 aligned with andnear the front opening 74 of the nozzle gate seal 73, and a rear end 71corresponding to the rear end 14 of the nozzle 10. Together the linersleeve 70 and the nozzle seal 73 form an annular melt channel 76 betweenthem that extends throughout the nozzle gate seal 73, and is in fluidcommunication with the radial melt channel 64. Preferably, the linersleeve 70 also has an angled flange 80 near the nozzle gate seal 73 todirect the flow of material from the radial melt channel 64 into theannular melt channel 76.

In addition, the liner sleeve 70 has a central bore 68 that extendsthroughout the body 12 and to the rear end 14 of the nozzle 10. Thecentral bore 68 of the liner sleeve 70 is designed to receive anelongated valve pin 110. The central bore 68 also defines a portion of acentral melt channel 78 for the flow of material around the valve pin110 and through the nozzle 10. As shown in FIG. 1, the annular meltchannel 76 is radially spaced from the central melt channel 78.

The valve pin 110 has a body 111, a head 112, and a front tip 116opposite the head 112. The front tip 116 may be either squared off, asshown in FIGS. 1, 4A-4E, and 5, or tapered (not shown). The front tip116 is also designed to fit within the front opening 74 of the nozzlegate seal 73. In addition, the valve pin 110 is capable of being movedforward and backward to several different positions, as described inmore detail below.

The front melt distribution manifold 18 is positioned on the manifoldlocator 88 between the nozzle retainer plate 20 and the rear meltdistribution manifold 94. The front melt distribution manifold 18 isheated by an integral electrical heating element 86 and has a front face16 that abuts against the rear end 14 of the nozzle 10. The front meltdistribution manifold 18 also has at least one bushing seat opening 50with a recessed portion 52 for receiving a valve bushing 98, and atleast one melt bore 104, with a diameter 104 a, in communication withthe central bore 68 of the liner sleeve 70. Like the central bore 68,the melt bore 104 is designed to receive the valve pin 110, and definesanother portion of the central melt channel 78 for the flow of materialaround the valve pin 110 and through the front melt distributionmanifold 18. Preferably, the front melt distribution manifold 18 has abushing seat opening 50 and a melt bore 104 for each nozzle 10 used inthe apparatus 5.

In addition, the front melt distribution manifold 18 has a first meltpassage 42 with an L-shaped melt portion 43 extending forward throughthe front melt distribution manifold 18 and in communication with theradial melt channel 64 of the nozzle 10. The melt portion 43 allowsmaterial to flow from the first melt passage 42 into the radial meltchannel 64 and then into the annular melt channel 76 of the nozzle 10.Accordingly, the melt portion 43, and thus the first melt passage 42, isin communication with the annular melt channel 76 through the radialmelt channel 64.

As shown in FIG. 1, a melt inlet nozzle 130 abuts against the front meltdistribution manifold 18 opposite the nozzle retainer plate 20. The meltinlet nozzle 130 has a central bore 132 partially defining a main meltpassage 134 that extends throughout the melt inlet nozzle 130 and intothe front melt distribution manifold 18. The main melt passage is influid communication with the first melt passage 42 of the front meltdistribution manifold 18 and an injection cylinder (not shown) forsupplying a virgin preform material 200, such as polyethyleneterephthalate (“PET”). The melt inlet nozzle 130 also has a heatingelement 136.

The front melt distribution manifold 18 also has a second melt passage44 with an L-shaped melt portion 45 extending backward through the frontmelt distribution manifold 18 and in communication with the bushing seatopening 50. The second melt passage 44 is also in communication with aninjection cylinder (not shown) for supplying a recycled preform material250, such as recycled PET. Recycled preform material is preferably usedsince it is less expensive, both economically and environmentally, thanvirgin preform material. The melt portion 45 allows the recycled preformmaterial to flow from the second melt passage 44 backward into the valvebushing 98 seated in the bushing seat opening 50, as explained in moredetail below.

The apparatus 5 also comprises a rear melt distribution manifold 94positioned on the manifold locator 88 between, but preferably spacedapart from, the front melt distribution manifold 18 and the back plate24, as shown in FIG. 1. The rear melt distribution manifold has acentral bore 95 for receiving the melt inlet nozzle 130. The rear meltdistribution manifold 94 also has a third melt passage 118 incommunication with an injection cylinder (not shown) for supplying abarrier material 300, such as nylon or ethylene vinyl alcohol (“EVOH”).The third melt passage 118 also has an L-shaped portion 119 extendingforward out the rear melt distribution manifold 94. In addition, therear melt distribution manifold 94 has a bushing bore 149 aligned withthe melt bore 104 of the front melt distribution manifold 18. Asdescribed in more detail below, the rear melt distribution manifold 94is heated by an integral electrical heating element 100 to a loweroperating temperature than the front melt distribution manifold 18, andthe air space 101 provided between the two manifolds 18, 94 providesthermal separation between them.

The apparatus 5 of the present invention also includes a valve bushing98 positioned between the manifolds 18, 94, and seated within thebushing seat opening 50 of the first melt distribution manifold 18. Inorder to facilitate its manufacture, the valve bushing 98 is preferablymade of a plurality of components that are brazed together to form asingle integral component. As shown in FIG. 1, the valve bushing 98 hasa tip protrusion 102 extending forwardly from a middle head portion 103into the recessed portion 52 of the front melt distribution manifold 18.Together, the tip protrusion 102 and the recessed portion 52 form anannular ring channel 106 between them, as shown in FIG. 2. The annularring channel 106 surrounds the central melt channel 78. The valvebushing 98 also has an elongated rear stem portion 148 extendingrearwardly from the middle head portion 103 through the bushing bore 149in the rear melt distribution manifold 94. A dowel pin 126 locatedbetween the middle head portion 103 and the front melt distributionmanifold 18 accurately retains the valve bushing 98 in place andprevents it from rotating.

The valve bushing 98 also has a central bore 108, which extends throughthe tip protrusion 102, the middle head portion 103, and the stemportion 148. As shown in FIG. 2, similar to the central bore 68 and themelt bore 104, the central bore 108 has a first diameter 108 a forreceiving the valve pin 110, and defining the a portion of the centralmelt channel 78 for the flow of material around the valve pin 110 andthrough the valve bushing 98. The first diameter 108 a of the centralbore 108 is preferably smaller, however, than the diameter 104 of themelt bore 104. The central bore 108 also has a second diameter 108 b forreceiving just the valve pin 110, and for preventing the flow ofmaterial rearwardly through the valve bushing 98.

As shown in FIG. 3, the central bore 108 of the valve bushing 98 and themelt bore 104 of the front melt distribution manifold 18 are joinedtogether with a flow extension 105, which also forms a portion of thecentral melt channel 78. The flow extension 105 has an annular flowopening 109 in communication with the annular ring channel 106.Preferably, the annular flow opening 109 is sized to be substantiallyequal to the difference between the diameters 104 a, 108 a of the meltbore 104 and the central bore 108, respectively. In other words, thewidth of the central melt channel 78 is preferably increased toaccommodate the additional material flow from the annular ring channel106, without interrupting or affecting the flow of other material in thecentral melt channel. It should also be understood that the amount ofmaterial flowing from the annular ring channel 106 may be controlled byincreasing (i.e., more flow) or decreasing (i.e., less flow) the size ofthe annular flow opening 109.

As shown in FIGS. 1-2, the valve bushing 98 has an L-shaped firsttransitional melt passage 122 and a second transitional melt passage 84.The first transitional melt passage 122 is aligned and in communicationwith both the melt portion 45 of the second melt passage 44 of the frontmelt distribution manifold 18, and an annular passage 123 in the middlehead portion 103 of the valve bushing 98. The annular passage 123 isalso in communication with the central bore 108 of the valve bushing 98,as best shown in FIG. 2. Accordingly, the melt portion 45, and thus thesecond melt passage 44, is in communication with the central meltchannel 78 through the first transitional melt passage 122 and theannular passage 123.

The second transitional melt passage 84 is in communication with boththe L-shaped portion 119 of the third melt passage 118 and an annularring groove 107 disposed around the tip protrusion 102 of the valvebushing 98. The annular ring groove 107 is also in communication withthe annular ring channel 106, as best shown in FIG. 2. Accordingly, theL-shaped portion 119, and thus the third melt passage 118, is incommunication with the annular ring channel 106 through the secondtransitional melt passage 84 and the annular ring groove 107.

The back plate 24 of the apparatus 5 of the present invention ispositioned on the manifold locator 88 next to the rear melt distributionmanifold 94 opposite the front melt distribution manifold 18. The backplate 24 has a central bore 25 aligned with the central bore 95 of therear melt distribution manifold 94 for receiving the melt inlet nozzle130. In addition, a locating ring 160 is preferably attached with one ormore bolts 162 to the back plate 24 opposite the rear melt distributionmanifold 94. The locating ring 160 also has a central bore 164 alignedwith the central bore 25 of the back plate 24 for receiving the meltinlet nozzle 130.

The back plate 24 preferably has a piston seat opening 150 aligned withthe bushing bore 149 of the rear melt distribution manifold 94. Anactuating mechanism 146 is positioned within the piston seat opening150. The actuating mechanism 146 comprises a piston cylinder 154 and anend cap 155 for connecting the head 112 of the valve pin 110 to thepiston cylinder 154. During operation of the actuating mechanism 146,the piston cylinder 154 and the end cap 155 may extend into a portion ofthe bushing bore 149, as shown in FIG. 1. The piston cylinder 154 ispreferably driven by controlled fluid pressure (i.e., from oil or water)applied through one or more ducts (not shown). It should be understoodthat while only a hydraulic actuating mechanism is described and shownherein, other types of actuating mechanisms, such as electro-mechanicalmechanisms, can be used with the apparatus of the present invention.

Driving the piston cylinder 154 forward causes the valve pin 110 to moveforward toward the cavity retainer plate 28. Moving the piston cylinder154 all the way forward causes the front tip end 116 of the valve pin110 to be seated within the front opening 74 of the nozzle gate seal 73,thereby cutting off fluid communication between the melt channels 76, 78and the front opening 74 of the nozzle gate seal 73. On the other hand,driving the piston cylinder 154 backward causes the valve pin 110 tomove backward away from the cavity retainer plate 28. Moving the pistoncylinder 154 backward past the front opening 74 of the nozzle gate seal73 causes the front tip end 116 of the valve pin 110 to be withdrawnfrom the front opening 74 of the nozzle gate seal 73, therebyestablishing fluid communication between the annular melt channel 76 andthe front opening 74 of the nozzle gate seal 73. In addition, moving thepiston cylinder 154 backward past the front opening 75 of the linersleeve 70 causes the front tip end 116 of the valve pin 110 movebackward past the front opening 75 of the liner sleeve 70, therebyestablishing fluid communication between not only the annular meltchannel 76 and the front opening 74 of the nozzle gate seal 73, but alsobetween the central melt channel 78 and the front opening 74 of thenozzle gate seal 73.

As shown in FIGS. 1 and 5, the cavity retainer plate 28 of the presentinvention has a cavity 36 around a mold core 37. The cavity 36 has acavity opening 38 aligned with the front opening 74 of the nozzle gateseal 73. The cavity 36 may have any number of shapes and configurationsdepending on the desired product to be molded. As shown in FIG. 1, thecavity preferably, but not necessarily, has the shape of a bottlepreform with a threaded end. It should be understood that by alteringthe cavity 36, one may mold other bottle preforms of different shapesand configurations, or products different from bottle preforms, such asclosures, and the present invention is not limited to the molding ofonly the bottle preform shown or even other types of preforms.

It should also be understood that the apparatus 5 of the presentinvention, especially its nozzles, may also have one or more heatingsystems, cooling systems, and insulative air spaces to maintain theproper temperatures for its components and the materials flowing throughthe apparatus. Examples of suitable heating systems, cooling systems,and insulative air spaces for the apparatus of the present invention aredescribed in U.S. patent application Ser. No. 08/969,764, entitled“Sprue Gated Five Layer Injection Molding Apparatus,” filed on Nov. 13,1997, as well as U.S. Pat. Nos. 5,094,603, 5,135,377, and 5,223,275 toGellert, which are all specifically incorporated in their entiretyherein by reference.

The operation of the apparatus of the present invention will now bedescribed with particular reference to FIGS. 4A-4E and 5. While theformation of only a four layer bottle preform is shown in the drawingsand described below, it should be understood that other types of fourlayer preforms or products different than preforms, such as closures,with different material characteristics, may be the resulting productsof the apparatus and method of the present invention.

As shown in FIG. 4A, the method of the present invention begins with thevalve pin fully inserted through the front opening 74 of the nozzle gateseal 73 by the forward motion of the piston cylinder 154. As a result,fluid communication between the annular melt channel 76, the centralmelt channel 78, and the front opening 74 of the nozzle gate seal 73 iscutoff. In this position, the valve pin is identified by the referencenumeral 110 a. Electrical power is then applied to the heating elements58, 86, 136 of the nozzle 10, the front melt distribution manifold 18,and the melt inlet nozzle 130, respectively, to heat them to anoperating temperature for the virgin preform material disposed withinthe main melt passage 134 and the first melt passage 42, and therecycled preform material disposed within the second melt passage 44. IfPET is used for the virgin and recycled preform materials, the preferredoperating temperature is about 565° F.

Next, the valve pin is pulled out of the front opening of the nozzlegate seal by the backward motion of the piston cylinder, as shown inFIG. 4B. As a result, fluid communication is established between theannular melt channel and the front opening of the nozzle gate seal, butnot between the central melt channel and the front opening of the nozzlegate seal. In this position, the valve pin is identified by thereference numeral 110 b.

Injection pressure is then applied to the main melt passage 134 to forcea first portion 200 a of virgin preform material through the first meltpassage 42 and into the melt portion 43. From there, the first portion200 a of virgin preform material flows through the radial melt channel64 aligned with the melt portion 43, into the annular melt channel 76,out the front opening 74 of the nozzle gate seal 73, and into the cavityopening 38. Injection pressure is applied until the first portion 200 aof virgin preform material fills the cavity 36, as shown in FIG. 4B. Thefirst portion 200 a of virgin preform material begins to cool as itfills the cavity 36.

Electrical power is then applied to the heating element 100 in the rearmelt distribution manifold 94 to heat it to an operating temperature forthe barrier material 300 disposed within the third melt passage 118. Ifnylon is used for the barrier material, the preferred operatingtemperature is about 400° F. Next, the valve pin is pulled out of thefront opening 75 of the liner sleeve 70 by the backward motion of thepiston cylinder, as shown in FIG. 4C. As a result, fluid communicationis established between not only the annular melt channel and the frontopening of the nozzle gate seal, but also between the central meltchannel and the front opening of the nozzle gate seal. In this position,the valve pin is identified by the reference numeral 110 c.

Injection pressure is then applied to the main melt passage 134 to forcea second portion 200 b of virgin preform material through the first meltpassage 42 and into its melt portion 43. From there, the second portion200 b of virgin preform material flows through the radial melt channel64 aligned with the first melt portion 43 and into the annular meltchannel 76. Injection pressure is also applied to the recycled preformmaterial 250 in the second melt passage 44 to force the recycled preformmaterial through the second melt passage 44 and into its melt portion45. From there, the recycled preform material 250 flows through theL-shaped first transitional melt passage 122 aligned with the meltportion 45 of the second melt passage 44, and into the annular passage123 of the valve bushing 98. The recycled preform material 250 alsoflows from the annular passage 123 into the central melt channel 78 andaround the valve pin 110 toward the cavity 36.

At about the same time, injection pressure is applied to the barriermaterial 300 in the third melt passage 118 to force the barrier materialthrough the third melt passage 118 and into its L-shaped portion 119.From there, the barrier material 300 flows into the second transitionalmelt passage 84, through the annular ring groove 107, and into theannular ring channel 106. As best shown in FIG. 3, the barrier material300 flows from the annular ring channel 106, through the flow opening109, and into the flow extension 105. The barrier material 300 thenjoins and surrounds the flow of the recycled preform material 250 in thecentral melt channel 78. Since the flow opening 109 is preferably sizedto be substantially equal to the difference between the diameters 104 a,108 a of the melt bore 104 of the front melt distribution manifold 18and the central bore 108 of the valve bushing 98, respectively, the flowof the barrier material does not interrupt the flow of the recycledpreform material. As a result, the flow pressure of the recycled preformmaterial before the flow extension is substantially the same as the flowpressure of the recycled preform material after the flow extension. Inaddition, since the barrier material flows together with the recycledpreform material through the central melt channel 78, as best shown inFIG. 5, degradation and pressure drop problems causes by too large ortoo small of channels for the barrier material are avoided.

Together, the barrier material 300 and the recycled preform material 250flow through the central melt channel 78 and around the valve pin 110,and out the front opening 75 of the liner sleeve 70. Here, the barriermaterial 300 and the recycled preform material 250 are joined andsurrounded by the second portion 200 b of the virgin preform materialflowing from the annular melt channel 76. At this point, the secondportion 200 b of the virgin preform material, the barrier material 300,and the recycled preform material 250 are all still hot. Together, thesecond portion 200 b of the virgin preform material, the barriermaterial 300, and the recycled preform material 250 simultaneously flowout the front opening 74 of the nozzle gate seal 73, and into the cavityopening 38. The simultaneous flow of these materials helps reduce thecycle or production time for the resulting perform. Next, the secondportion 200 b of the hot virgin preform material, the hot barriermaterial 300, and the hot recycled preform material 250 split the firstportion 200 a of the cooled virgin preform material in the cavity 36, asshown in FIGS. 4C and 5. Injection pressure is applied to the first,second, and third melt passages 42,44, 118 until the cavity 36 iscompletely filled with material.

As best shown in FIG. 5, the barrier material 300 is surrounded by, andembedded within, the second portion 200 b of hot virgin preform materialand the hot recycled preform material 250 as the barrier material 300flows into the cavity 36. As a result, the second portion 200 b of hotvirgin preform material and the hot recycled preform material 250insulate the barrier material 300 from the first portion 200 a of cooledvirgin preform material already in the cavity 36. This arrangementprovides an evenly and uniformly distributed layer of barrier materialwithin the resulting preform.

In addition, since the barrier material 300 is surrounded by the secondportion 200 b of the hot virgin preform material and the hot recycledpreform material 250, the distribution and position of the barriermaterial 300 within the cavity is properly controlled. In other words,the distribution and positioning of the barrier material 300 is notsolely dependent on the cavity, the mold core, and/or the cooled preformmaterial already present in the cavity. Instead, the distribution andpositioning of the barrier material for the cavity, and thus theresulting preform, is controlled and balanced by the melt channelsbefore the barrier material enters the cavity 36. The position of thebarrier material within the cavity, and thus the resulting preform, mayalso be set and controlled by manipulating the timing, temperature, andpressure as known in the art. This arrangement ensures that the barriermaterial will be correctly positioned and balanced within the cavity,and avoids the unbalanced distribution and positioning of the barriermaterial within the cavity that can be caused, for example, bymisalignment or shifting of the mold core 37.

After the cavity 36 is filled, the valve pin is moved forward by thepiston cylinder to cutoff material flow and fluid communication betweenthe central melt channel and the front opening of the liner sleeve, asshown in FIG. 4D. As shown in FIG. 4E, the piston cylinder continues tomove the valve pin forward until the valve pin is fully inserted intothe front opening of the nozzle gate seal, thereby also cutting offmaterial flow and fluid communication between the annular melt channeland the front opening of the nozzle gate seal. Since the valve pin shutsoff the flow of material out of the nozzle, it is not necessary torelease the injection pressure applied to the preform or barriermaterials. Once the cavity is filled and the material flow has stopped,the preform continues to cool until the material has solidified enoughto be ejected from the cavity.

As a result of the apparatus and method of the present invention, abottle preform 170 may be created, as shown in FIG. 6. The bottlepreform 170 has a first open end 171 and a second closed end 172 spacedfrom and opposite of the first open end. Preferably, but notnecessarily, the first open end 171 has threads 173. The bottle preform170 also has an outer layer 174 of virgin preform material, such asvirgin PET, an inner layer 175 of virgin preform material, such asvirgin PET, a core layer 176 of barrier material, such as nylon or EVOH,between the outer and inner layers 174, 175 of virgin preform material,and an intermediate layer 177of recycled preform material, such asrecycled PET, between the core layer 176 of barrier material and theinner layer 175 of virgin preform material. The core layer 176 ofbarrier material and the intermediate layer 177 of recycled preformmaterial preferably extend substantially throughout the bottle preform170, as shown in FIG. 6. Each layer 174, 175, 176, 177 has severalproperties, including, but not limited to, thickness, weight, andpercentage of total volume (“volume percentage”).

By altering the timing and/or the amount of preform or barrier material,the properties of the outer, inner, core, and intermediate layers 174,175, 176, 177 may also be altered. For instance, by injecting a largeramount of the first and/or second portions 200 a, 200 b of the virginpreform material into the cavity 36, thicker and heavier outer and/orinner layers 174, 175 of virgin preform material may be formed. Assuminga constant total volume for the cavity, and thus the bottle preform 170,the volume percentage of the virgin preform material will be increased,while the volume percentage of the barrier material 300 and the recycledpreform material 250 will be decreased. On the other hand, by injectinga larger amount of barrier material into the cavity, a thicker andheavier core layer 176 of barrier material may be formed. Assuming onceagain a constant total volume for the cavity, and thus the bottlepreform, the volume percentage of the barrier material will beincreased, while the volume percentage of the virgin and recycledpreform materials will be decreased. Similarly, a thicker and heavierintermediate layer 177 of recycled preform material may be formed byinjecting a larger amount of recycled preform material into the cavity.With a constant total volume for the cavity, and thus the bottlepreform, the volume percentage of the recycled preform material will beincreased, while the volume percentage of the barrier and virgin preformmaterials will be decreased.

As a result of the apparatus and method of the present invention, aclosure 180 may also be created, as shown in FIG. 7. The closure 180 maybe made with the same apparatus and method as the bottle perform 170,with the exception that the preform material (i.e., PET) is preferablyreplaced with a closure material, such as polypropylene. The closure 180has a base 181 and an annular flange 182 extending outward from thebase. The annular flange 182 has an inner side 183, preferably, but notnecessarily, with threads 184. The closure 180 also has an outer layer185 of virgin closure material, such as virgin polypropylene, an innerlayer 186 of virgin closure material, such as virgin polypropylene, acore layer 187 of barrier material, such as nylon or EVOH, between theouter and inner layers 185, 186 of virgin closure material, and anintermediate layer 188 of recycled closure material, such as recycledpolypropylene, between the core layer 187 of barrier material and theinner layer 186 of virgin closure material. The core layer 187 ofbarrier material and the intermediate layer of recycled closure materialpreferably extend substantially throughout the base 181 of the closure180, as shown in FIG. 7. Each layer 185, 186, 187, 188 has severalproperties, including, but not limited to, thickness, weight, andpercentage of total volume (“volume percentage”).

By altering the timing and/or the amount of closure or barrier material,the properties of the outer, inner, core, and intermediate layers 185,186, 187, 188 may also be altered. For instance, by injecting a largeramount of the first and/or second portions of the virgin closurematerial into the cavity, thicker and heavier outer and/or inner layers185, 186 of virgin closure material may be formed. Assuming a constanttotal volume for the cavity, and thus the closure 180, the volumepercentage of the virgin closure material will be increased, while thevolume percentage of the barrier material and the recycled closurematerial will be decreased. On the other hand, by injecting a largeramount of barrier material into the cavity, a thicker and heavier corelayer 187 of barrier material may be formed. Assuming once again aconstant total volume for the cavity, and thus the closure, the volumepercentage of the barrier material will be increased, while the volumepercentage of the virgin and recycled closure materials will bedecreased.

As an alternative to the valve-gated apparatus 5 shown in FIGS. 1-5 anddescribed above, FIG. 8 shows a preferred embodiment of a portion of athermal-gated, multi-cavity injection molding apparatus 405 of thepresent invention. The apparatus 405 is identical to, and operates inthe same manner as, the apparatus 5, with only a few exceptions. Toavoid redundancy and unnecessary repetition, only the differencesbetween the apparatus 405 and the apparatus 5 will be discussed indetail below. Similarly, for ease of illustration, only some of thecomponents of the apparatus 405 are identified by reference numerals inFIG. 8. Preferably, the non-identified components of the apparatus 405are identical to the corresponding components of the apparatus 5. Inaddition, it should be understood that, like the apparatus 5, theapparatus 405 may be used to create both the bottle preform 170 and theclosure 180 shown in FIGS. 6-7 and described above.

The primary difference between the apparatus 405 and the apparatus 5 isthat the apparatus 405 does not have a valve pin. As a result, theapparatus 405 is manipulated by controlling the injection pressureapplied to the first and second melt passages, rather than bycontrolling the valve pin. In other words, instead of moving a valve pinforward and backward to cutoff and establish the flow of material, theapparatus 405 uses increases and decreases in the injection pressure tocutoff or establish the flow of material. Otherwise, the operation andmethod of the apparatus 405 is the same as the operation and method ofthe apparatus 5.

Since the apparatus 405 does not use a valve pin, certain components ofthe apparatus 5 are no longer necessary for the apparatus 405. Forinstance, the back plate 424 of the apparatus 405 does not have a pistonseat opening 150 or an actuating mechanism 146. Likewise, the rear meltdistribution manifold 494 of the apparatus 405 does not have a bushingbore 149. Moreover, the valve bushing 498 of the apparatus 405 does nothave a stem portion 148, and the valve bushing 498 has a central bore508, with only one diameter 108 a, that does not extend past the annularpassage 123.

FIG. 9 shows a partial view of another embodiment of a front meltdistribution manifold 618 of the present invention. The front meltdistribution manifold 618 is identical to, and operates in the samemanner as, the front melt distribution manifold 18 described above andshown in FIGS. 1 and 8, with only a few exceptions. In order to avoidredundancy and unnecessary repetition, only the differences between thefront melt distribution manifold 618 and the front melt distributionmanifold 18 will be discussed in detail below.

As shown in FIG. 9, the front melt distribution manifold 618 comprises abridge section 705, a sub-manifold section 710 spaced from the bridgesection 705, and a melt link 715 joining the bridge section 705 and thesub-manifold section 710. The bridge section 705 has a bridge passage707 in communication with the main melt passage 134 of the melt inletnozzle 130, the sub-manifold section 710 has a sub-manifold passage 713in communication with the first melt passage 42, and the melt link 715has a link passage 717 in communication with both the bridge passage 707and the sub-manifold passage 713. An example of a suitable melt link foruse with the present invention is disclosed in U.S. Pat. No. 5,843,361,specifically incorporated herein by reference.

A conventional melt mixer 719 (or static mixer) is also positioned inthe link passage 717, as shown in FIG. 9. During operation of thepresent invention, the use of PET for the preform material may generatea certain amount of undesirable acetaldehyde (“AA”). In addition,non-uniform shear stress may take place during the flow of the preformmaterial or the barrier material through the melt channels of themanifolds and/or the nozzle. This non-uniform shear stress can create anon-uniform temperature distribution across the preform or barriermaterial, thereby creating difficulties with uniformly filling thecavity 36 with the preform and the barrier material. The melt mixer 719,however, addresses these problems and helps to prevent them fromoccurring or reduce their effects. Specifically, the melt mixer 719helps reduce the amount of AA generated and improve the temperatureuniformity across the material flow. Any of the melt mixers or staticmixers known in the prior art may be adapted for use with the presentinvention. Examples of suitable melt mixers or static mixers aredisclosed in U.S. Pat. Nos. 4,541,982, 4,965,028, 5,262,119, andApplicant's DE 3201710 application, all of which are specificallyincorporated herein by reference.

Although a melt mixer is shown only in the link passage of the melt linkfor the front melt distribution manifold, it should be understood thatmelt mixers or static mixers may be used in a number of differentlocations throughout the apparatus of the present invention. Forinstance, a melt mixer may be positioned in a link passage of a meltlink for the rear melt distribution manifold 94. In addition, meltmixers may be positioned in the transitional melt passages 84, 122 ofthe valve bushing 98 and/or in the radial melt channel 64 of the nozzle10.

As shown in FIG. 10, one or more melt mixers may also be positioned inthe central melt channel 78 of the thermal-gated injection moldingapparatus 405 shown in FIG. 8 and described above. Preferably, a firstmelt mixer 719 a is positioned in the central melt channel 78 near theannular ring channel 106 for mixing the barrier material 300 with therecycled preform material 250. Additionally, or alternatively, a secondmelt mixer 719 b is also preferably positioned in the central meltchannel 78 near the front opening 74 of the nozzle gate seal 73 formixing the barrier material 300 with the recycled preform material 250.While both the first and second melt mixers 719 a, 719 b are shown inFIG. 10, it should be understood that only one or the other, or both,may be used with the thermal-gated injection molding apparatus of thepresent invention.

The apparatus and methods of the present invention may be applied withparticular advantage to preforms and closures for bottles or containers.The four-layer preforms and closures formed by the apparatus and methodsof the present invention provide reliable molded products for protectingtheir contents. Moreover, the use of a recycled preform material reducesthe cost of manufacturing the preforms and closures.

It should also be readily apparent from the forgoing description andaccompanying drawings that the injection molding apparatus and method ofthe present invention are an improvement over the prior art. Forinstance, the apparatus and method of the present invention do notrequire multiple melt inlets, passages, channels, and gates. Instead,the apparatus and method of the present invention only uses twoinjection cylinders, two melt passages, and one gate to createfour-layer preforms and closures. As a result, the present inventionovercomes the disadvantages associated with the prior art injectionmolding devices and methods by providing a multi-layer injection moldingapparatus and method that are relatively simple and inexpensive to bothoperate and manufacture.

The present invention also overcomes the disadvantages of the prior artinjection molding devices and methods by surrounding the barriermaterial with hot preform material before injecting it into the cavity,thereby avoiding injection of the barrier material directly against acooled portion of preform material previously disposed in the cavity.Consequently, the present invention provides a four-layer perform andclosure with a more evenly and uniformly distributed barrier layer withbetter protection characteristics. Similarly, unlike the prior art,since the present invention injects the barrier material simultaneouslywith its surrounding hot preform material, rather than after firstinjecting hot preform material into the cavity, the cycle time for thepreforms or closures is minimized and not increased.

Those skilled in the art to which the invention pertains may makemodifications and other embodiments employing the principles of thisinvention without departing from its spirit or essentialcharacteristics, particularly upon considering the foregoing teachings.For instance, the threads of the bottle preform and/or the closure maybe eliminated entirely or replaced with some other fastening feature. Inaddition, any desirable shape and configuration may be used for thecavity and the resulting bottle preform and/or closure, depending onmanufacturing and consumer preferences. Likewise, manufacturing andconsumer preferences may also dictate the timing and number of cyclesfor the operation of the apparatus and methods of the present invention.Also, the recycled preform material may be replaced with another preformmaterial, a barrier material, or a mixture of both. Accordingly, thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive and the scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. Consequently, while the invention has been described withreference to particular embodiments, modifications of structure,sequence, materials and the like would be apparent to those skilled inthe art, yet still fall within the scope of the invention.

What is claimed is:
 1. An injection molding apparatus for multi-layermolding comprising: a central melt channel having a first portion forflow of a first material, a second portion for flow of the firstmaterial and a second material, a flow extension connecting the firstportion and the second portion, the flow extension having a flowopening, and at least a portion of the central melt channel being in anozzle and in communication with a front opening in the nozzle; anannular ring channel around the central melt channel for flow of thesecond material, the annular ring channel being in communication withthe flow opening of the flow extension; and an annular melt channelradially spaced from the central melt channel for flow of a thirdmaterial, the annular melt channel being in communication with thecentral melt channel near the front opening in the nozzle; wherein thefirst and second materials flow together through the entire portion ofthe central melt channel in the nozzle.
 2. The injection moldingapparatus of claim 1 wherein the first portion of the central meltchannel has a first diameter, and the second portion of the central meltchannel has a second diameter greater than the first diameter.
 3. Theinjection molding apparatus of claim 1 further comprising a cavity forreceiving flow of the first material and the second material from thecentral melt channel simultaneously.
 4. The injection molding apparatusof claim 1 further comprising a moveable valve member positioned withinthe central melt channel, the moveable valve member capable of cuttingoff flow of the first and second materials from the central meltchannel.
 5. The injection molding apparatus of claim 1 furthercomprising a melt mixer.
 6. The injection molding apparatus of claim 1wherein the second portion of the central melt channel maintains flow ofthe first material and flow of the second material in a side-by-sideorientation.